1994 F150 computer

Hello all, I am in need of help with my truck. I need to get a new ECU, but when I took mine out to look inside of it I put it back in the garage, not the truck. When I moved out of state for college my dad cleaned out the garage and apparently moved or threw out the computer, so I don't have the code to but the correct one. I can get the VIN number, but it is a 1994 F150 4x4 XL with the 300 4.9l I6, M50D manual transmission and manual transfer case. Can anybody help me get the right code for the computer?????